High pressure containers



c- 5, 1962 J. GRATZMULLER 3,070,127

HIGH PRESSURE CONTAINERS Filed May 28, 1958 4 Sheets-Sheet 1 4 QWVB 1962 J. L. GRATZMULLER HIGH PRESSURE CONTAINERS 4 Sheets-Sheet 2 Filed May 28, 1958 FIG.2

FIG.3

Dec. 25, 1962 J. GRATZMULLER 3,070,127

HIGH PRESSURE CONTAINERS 4 Sheets-Sheet 8 Filed May 28, 1958 FIG.4-

Dec. 25, 1962 J. L. GRATZMULLER HIGH PRESSURE CONTAINERS 4 Sheets-Sheet 4 Filed May 28, 1958 FIG.5

United States Patent 3,070,127 HIGH PRESSURE CONTAINERS Jean Louis Gratzmuller, 66 Blvd. Maurice Barres, Neuilly-sur-Seine, France Filed May 28, 1958, Ser. No. 811,242 8 Claims. (Cl. 138--31) The present invention relates to high-pressure fluid containers, such as oleo-pneumatic accumulators and bottles for holding compressed gases.

It is an object of the invention to considerably reduce the cost price of such containers Without detriment to safety.

The most economical method for the manufacture of containers of this kind consists in using a body constituted by a cylindrical tube having a thickness substantially uniform throughout its length, such a tube being easily obtainable by a mere drawing operation followed by a cutting operation to provide a tube of the required length, whereafter the inner surface of the tube is machined.

To form a container it is then sufiicient to close the tube at its ends by providing it with fluid-tight end pieces or closure members, at least one of which is easily removable. The other end-piece may optionally be made integral with the cylindrical tube, though an embodiment with two removable closure members will probably be cheaper.

In a combination, as above, the removable closure members must be positively prevented from being accidentally ejected, under all conditions of pressure likely to occur inside the container. This, of course, prevents accidents which might otherwise occur from the forceable expulsion of the closure members from the container.

From an economical point of view, the cost price of the cylindrical body of the container is a function of the Weight of the metal thereof and, therefore, of the thickness of the tubular wall. It is desirable, therefore, to make the wall only as thick as necessary.

A further object of the invention is to provide a container of the above-mentioned type, in which the thickness of the cylindrical tube constituting the body of the container is sufficient for withstanding the maximum service pressure, multiplied by such safety factor as may be specified for the particular function of the container. Furthermore, means for removab-ly securing the endpieces to the container body are such that, on continued increase of internal pressure, the container will fail by rupture of the cylindrical body along one of its generatrix lines earlier than failure of the means securing the removable end closure members.

The conventional means used for securing an end-piece to a tubular container is by screw-threaded engagement. However, screw threads are relatively expensive to make, and it is desirable to avoid their use in making a cheap container. Moreover, the thinner the tubular wall the more difficult it is to cut screw threads thereon.

According to this invention, a high pressure fluid container comprises a tubular cylindrical body with endclosure means, at least one of which is removable. The end closure means comprises a disc-like closure member freely slidable in the tubular body and provided with annular pressure-tight sealing means, at least two annular abutment members, or assemblies of members, supported in circumferential grooves formed in the inner surface of the tubular body, a sleeve or sleeves slidable axially on the closure member and serving to retain and compress the sealing means, having formed thereon annular shoulders which bear on the exposed parts of the annular abutment members (or assemblies) with or without the interposition of another annular member,

such annular shoulders being axially spaced and both being remote from that side of the sealing means which is subjected to the internal pressure in the container.

Preferably, the container further includes an external reinforcing sleeve or sleeves surrounding the tubular container and extending axially so as to overlap the removable end closure means.

This reinforcement is desirable, not only because the grooves in which the annular abutment members are lodged reduce the wall thickness of the tubular body, but because the change of section at the grooves gives rise to stress-concentrations. It is important that this reinforcement be strong enough to ensure that if failure does occur (under excessive internal pressure) it will not be by belling of the ends of the tubular body which would allow the closure member to be blown out, but

rather by bulging and rupture of the middle Part of the tubular body. Experimental evidence of the achievement of this objective has been obtained as hereinafter shown.

The depth of the grooves in which the abutment members are lodged should not exceed half the normal wallthickness of the tubular body.

By using two axially spaced abutment members the end load due to the internal pressure is transmitted to the tubular casing in distributed fashion, and owing to elastic and plastic deformation of the material under load, the end load will be resisted approximately equally by the two abutment members.

At least one of the annular abutment members is preferably a piano-wire snap ring, this form of abutment being both efiicient and cheap.

As hereinafter shown, a removable end closure for the tubular body of a pressure-fluid container constructed as herein described lends itself to easy and rapid dismantling and reassembly.

The accompanying drawings illustrate by way of example only one embodiment of the invention as applied to an oleo-pneumatic accumulator together with certain detail modifications thereof. In the drawings:

FIGURE 1 is a partly fragmentary axial section of the accumulator;

FIGURES 2 and 3 are axial sections of one end closure of the accumulator illustrating modified forms of end closures;

FIGURE 4 is an end view illustrating a method of assembling the elements of an abutment ring in the tubular body of the accumulator; and

FIGURE 5 is a perspective view of the accumulator, partly broken away, illustrating the type of failure to be expected under excessive internal pressure.

Referring to FIGURE 1, the accumulator comprises a cylindrical tubular body 1, having a wall thickness which is capable of withstanding the maximum anticipated internal service pressure in the accumulator multiplied by an appropriate factor of safety.

In the body 1 slides a free piston 2, which in the illustrated example is constructed as described in US. Patent No. 2,724,412 and is sealed by a multiple seal 3 as described in US. Patent No. 2,847,262.

The ends of the tubular body 1 are closed by removable members 4, 6. Member 4 encloses the pneumatic chamber of the accumulator and is provided with an inflation device 5, which in this example is as described in US. Patent No. 2,804,094. Member 6 enclosing the hydraulic chamber of the accumulator has a central screwthreaded opening 7 adapted to receive a union for connection to an hydraulic service line.

The end closure members 4 and 6, which are of considerable axial thickness, can slide in the tubular body 1 and are sealed by deformable sealing rings 9 as described in U.S. Patent No. 2,804,094, positioned between a radial shoulder of the member 4 (or 6), the inner face of the tubular body 1, the cylindrical face 11 of the reduceddiameter portion of the member 4 (or 6) which ends at the shoulder and a sleeve 10, which has a sliding fit in the tubular body and on the clindrical face 11, and is retained in the way hereinafter described. The internal pressure in the accumulator (at each end) thus compresses the ring9 between the shoulder of member 4 (or 6) and the sleeve 10 and causes it to spread radially and seal tightly against the inner face of the tubular body 1 and the cylindrical face 11.

Sleeve 10 is retained in the tubular body 1 against the internal pressure by means of a piano-wire circlip 12 and a segmental abutment ring 14 of rectangular cross:

.but not greater than half the wall thickness of the body 1. Groove 15 is of rectangular section and fits the ring 14 closely. The sleeve 10 is of stepped cross section comprises an inclined shoulder 16 which bears against the exposed part of the circlip 12, which in turn bears against an inclined face 17 of the groove 13, and a radial shoulder which bears against the exposed part of the ring 14. The provision of the inclined bearing faces 16', 17 ensures that the circlip 12 does not bear on the edges of the shoulder 16 and groove 13, which therefore cannot become burred by crushing and thus impede dismantling of the end closure assembly. The end closure assembly is finally completed by an external sleeve 18 which extends axially from a point well beyond the sealing ring 2 at one end to well beyond the segmental ring 14 on the other end to reinforce the tubular body 1 against hoop stresses. The sleeve 18 need only have, initially, a light frictional fit on the tubular body, since such a fit is sufficient to keep the circumferential expansion of the tubular body under the internal pressure loading well within the elastic limit until the tubular body and the reinforcing sleeve 18 become equivalent to a single member over which the hoop stress is distributed in accordance with St. Venants well known theory. Since the total thickness of the tubular body 1 and sleeve 18 is small compared with their mean diameter, the hoop stress in both these members will be nearly equal.

, The full benefit of the double abutment provided by the circlip 12 and segmental ring 14 is obtained when both are equally loaded, but it is not necessary to machine the sleeve 11 and grooves 13, 15 to such fine tolerances that their loading is equal as soon as any internal pressure is applied, because, as the internal pressure is increased to its maximum working value, the loading will automatically become equalized by a slight deformation of the bearing surface which first resists the load, provided of course that the machining tolerances are not excessive.

The circlips 12 are assembled in their grooves 13 by being sprung into place in the usual Way after the assembly 4 (or 6), 9, 11 has been inserted in the tubular body 1 and slid inwards to expose groove(s) 13. The

segmental rings 14 are then assembled in groove 15.

The method of assembling the rings 14 in their grooves 15 is illustrated in FIGURE 4.

Each ring 14 is made in three segments 25, 26, 27, preferably cut from a single bar and subsequently bent to the required radius of curvature. The total angular length of the three segments when placed end to end is less than 360, the angular lengths of the individual segments being preferably equal. This enables the third segment, such as 25, to be fitted into the groove 15 after the first two, 26 and 27, have been so fitted. In FIGURE 4, the position of segment 25, after fitting of the segments 26, 27 and before it has itself been inserted in the groove 15, is indicated at 28 in chain-dotted outline and by hatching. The gap left between segments 25 and 26 when all three segments have been fitted into the groove is finally filled by means of a key 29, which, as illustrated, is rectangular. To facilitate insertion, key 29 may have a trapezoidal plan form with one side being of a length just fitting the gap between segments 25 and 26 and the opposite side being slightly shorter. Such a key will be inserted with its shorter side in the groove 15.

Dismantling of the end closure assemblies is effected by reversing the assembly procedure.

In the modification illustrated in FIGURE 2, the segmental ring 14 of FIGURE 1 is replaced by a second circlip 12a similar to the circlip 12 and supported in a groove of the tubular body similar to groove 13 of FIG- URE 1. The sleeve 10 of FIGURE 1 is replaced by two similar sleeves 1t and 10a, stacked one on the other, and each having a single inclined shoulder similar to shoulder 16 of FIGURE 1 bearing on the circlips 12 and 12a respectively. This form of construction facilitates the assembly of the circlips, since circlip 12 can be sprung into its groove before the second sleeve 10a is put into place. In other respects the construction of FIGURE 2 is the same as that of FIGURE 1.

The modification illustrated in FIGURE 3 employs two circlips 12 and 12a as in FIGURE 2, but the sleeve 10 is not duplicated. Instead it is of stepped form having two inclined shoulders, one of which bears directly on the circlip 12 and the other on a piano-wire ring 24, which in turn bears on the circlip 12a. Assembly takes place as follows:

The closure member 4 or 6 (FIGURE 1) with the sealing ring 9 and sleeve 10 fitted on to it is slid into the tubular body far enough to expose the groove which is adapted to accommodate the circlip 12, the latter then being sprung into its groove. The piano-wire ring 24 is then placed on the sleeve 10, and finally the circlip 12a is spring into its groove in the tubular body. Dismantling is effected in the reverse order.

FIGURE 5, which is substantially a reproduction of a photograph taken after a test to destruction of specimen accumulator (as illustrated in FIGURE 1, but with the floating piston 2 removed) illustrates how, when the internal pressure becomes excessive, failure takes place by bulging and ultimate rupture, along an axially disposed crack, of the tubular body 1, under tensile hoop stress, before any noticeable distortion of the ends of the tubular body, or dislocation of the end closure assemblies occurs.

It will be observed that in the illustrated embodiments the force of the internal pressure is transmitted to the abutment elements 12, 14 (or 12, 12a) through the sealing ring 9, because the sleeve 10 (or sleeves 10, 10a) are axially slidable on the end closure member 4 (or 6).

Alternatively however, the force of the internal pressure may be transmitted to the abutment elements directly by the closure member, by eliminating the slidable sleeve 10 (or 10, 10a) and forming the shoulders which bear on the abutment elements, such as 12, 14 (FIG- URE 1) or 12, 24 (FIGURE 3) on the closure member (4 or 6) itself, the sealing means corresponding to the sealing ring 9 of FIGURE 1, being supported in a circumferential groove formed in the closure member. This provides a more conventional sealing arrangement in which the sealing means is not axially compressed and thus caused to expand radially, but derives its scaling properties from its intrinsic characteristics.

What is claimed is:

1. In a fluid pressure cylinder having an open end, the combination comprising a disc-shaped closure member slidable in said cylinder and including an outwardly projecting axial extension bounded laterally by a cylindrical surface, an annular packing element on said axial extension adapted to form a seal with the inner wall of said cylinder, a sleeve member slidable on said extension and providing an annular inwardly facing contact surface for engagement by said packing element, there being two axially spaced annular grooves provided in the inner wall of said cylinder near said open end thereof, an annular abutment member housed in each of said grooves, and two axially spaced annular shoulders on said sleeve member to bear on said abutment members when said closure member is urged by internal fluid pressure towards said open cylinder end.

2. The combination according to claim 1, in which said annular abutment members are piano-wire snap rings.

3. The combination according to claim 1, in which the annular shoulder of said sleeve nearest the packing element bears directly on the corresponding abutment member and the other shoulder is stepped radially inwards from the first-mentioned shoulder and bears indirectly on the corresponding abutment member through an intermediate piano-wire snap ring.

4. The combination according to claim 1, in which the annular abutment member remote from said packing element is an assembly of segmental members of rectangular section, whose axial dimension exceeds their radial dimensien, said segmental members occupying less than 360 of the groove in which they are housed, the gap covered by the otherwise unoccupied part of the groove being filled by a key.

5. The combination according to claim 1, in which said sleeve member is constituted by two mutually abutting rings slidable on said axial extension.

6. The combination according to claim 1, in which said abutment members bear against an inclined surface of said shoulders and an inclined surface of said grooves.

7. The combination according to claim 1, further including an external reinforcing sleeve surrounding the open end of said cylinder and extending axially so as to overlap said closure member at both its ends, the inner Wall of said reinforcing sleeve being a close fit over the outer wall or said cylinder.

8. A hydropneumatic accumulator comprising a cylinder, a first disc-shaped closure member movable in said cylinder for closing one end thereof, a second disc-shaped closure member movable in said cylinder for closing the other end thereof, a partition slidably mounted in said cylinder between said first and said second closure members to divide said cylinder into a liquid pressure chamber and a gas pressure chamber, said first closure member including means for connecting said liquid pressure chamber to a hydraulic system and said second closure member including means permitting introduction of gas under pressure into said gas pressure charnber, each of said first and second closure members including an outwardly projecting axial extension bounded laterally by a cylindrical surface, an annular packing element on said axial extension adapted to form a seal with the inner wall of said cylinder, and a sleeve member slidably mounted on said extension and providing an annular inwardly facing contact surface for engagement by said packing element, two axially spaced annular grooves, provided in the inner wall of said cylinder near said one end thereof, two axially spaced annular grooves provided in the inner Wall of said cylinder near said other end thereof, an annular abutment member housed in each of said four grooves, and two annular shoulders formed on each sleeve member to bear on the exposed parts of the corresponding abutment members when said closure members are urged towards the corresponding cylinder ends by the gas under pressure introduced into said gas pressure chamber.

References 'Cited in the tile of this patent UNITED STATES PATENTS 2,436,407 Stephens Feb. 24, 1948 2,651,385 Clark et al. Sept. 8, 1953 2,683,467 Greer July 31, 1954 2,817,361 Mercier Dec. 24, 1957 2,870,791 Wells et al. Jan. 27, 1959 2,880,746 Bernotas Apr. 7, 1959 2,934,093 Bleasdale Apr. 26, 1960 

